Aqueous treatment fluid and method of use

Abstract

A composition designed for dissolution or dispersion in water to give an aqueous treatment fluid having a yield point of zero, at a temperature between about 85 DEG and about 160 DEG F., which is compatible with cement slurries and with drilling muds and a method of using same to displace a drilling mud from a borehole which penetrates a subterranean formation, particularly immediately preceding the injection of a fluid such as a cement slurry, and which also exhibits good fluid loss control and may be adapted for use with either water-based or oil-based drilling muds. The composition comprises three components, a water soluble viscosifier which increases the viscosity of water under mixing and handling conditions but which becomes substantially insoluble in water when exposed to temperatures encountered downhole in a wellbore; a second component, a thickener, which is soluble or dispersible in and which increases the viscosity of water at temperatures experienced under downhole conditions; and a third component, a dispersant, which enhances the dispersibility of the first component in water and thereby permits it to go smoothly into solution. The composition optionally comprises a nonionic surfactant which may be added to improve the compatibility with an oil-based drilling mud of an aqueous treatment fluid prepared from the composition. The composition also optionally comprises a weighting agent to impart increased density to a treatment fluid prepared therefrom. When combined with water, the resultant aqueous treatment fluid, at a temperature between about 85 DEG and about 160 DEG F., has a kinematic viscosity of greater than about 0.1 and less than about 7.5 centipoise-gallons/pound.

I claim: 
     
       1. In a method for injecting a fluid into a borehole containing a drilling mud, wherein the fluid is not compatible with the mud and wherein injection of said fluid is preceded by injection of a composition compatible with both the mud and the fluid, the improvement comprising: injecting a sufficient quantity of said composition to separate said mud and said fluid, at an injection velocity which exceeds the critical velocity for said composition in the borehole at the bottom hole circulating temperature of said borehole, where the composition comprises an aqueous treatment fluid which has a yield point of zero at a temperature between about 85° and about 160° F. and is compatible with cement slurries and drilling muds employed in the completion and drilling of subterranean boreholes, which treatment fluid comprises: Component (A) A viscosifier which is soluble in and increases the kinematic viscosity of water at temperatures between about 40° and about 100° F. and which becomes substantially insoluble in said treatment fluid at a temperature between about 85° and about 160° F.;   Component (B) A thickener which is different than Component (A) and is soluble or dispersible in and increases the kinematic viscosity of water at temperatures between about 40° and about 160° F.;   Component (C) A dispersant which enhances the dispersibility of Component (A) in water;   Component (D) A weighting agent; and   Component (E) Water; wherein said Components are present in amounts sufficient to impart a kinematic viscosity to said treatment fluid, at a temperature between about 85° and about 160° F., of greater than about 0.1 and less than about 7.5 centipoise-gallons/pound.     
     
     
       2. The method of claim 1 wherein the fluid injected comprises an aqueous cement slurry. 
     
     
       3. The method of claim 1 wherein the mud is a water-based mud. 
     
     
       4. The method of claim 1 wherein the mud is an oil-based mud and the composition further comprises Component (F), a nonionic surfactant, in an amount sufficient to render the treatment fluid compatible with said oil-based mud. 
     
     
       5. The method of claim 2, 3 or 4 wherein Component (A) of the treatment fluid compires a hydroxypropylcellulose and Component (B) comprises a carboxymethylcellulose and a water-swellable extender. 
     
     
       6. The method of claim 5 wherein the kinematic viscosity of the aqueous treatment fluid is between about 0.3 and about 6.5 centipoise-gallons/pound. 
     
     
       7. The method of claim 3 or 4 wherein the fluid injected comprises an aqueous hydraulic cement slurry. 
     
     
       8. The method of claim 7 wherein the fluid is injected at a flow rate of from about 1 to about 12 barrels per minute. 
     
     
       9. The method of claim 8 wherein the bottom hole circulating temperature (B.H.C.T.) is between about 85° and about 350° F. 
     
     
       10. The method of claim 9 wherein the B.H.C.T. is between about 150° and about 250° F. 
     
     
       11. The method of claim 9 wherein the B.H.C.T. is between about 125° and about 145° F. 
     
     
       12. The method of claim 7 wherein said fluid injected is thixotropic. 
     
     
       13. The method of claim 7 wherein the aqueous treatment fluid further comprises sodium chloride in an amount of about 1 to about 18 percent, based on the weight of Component (E). 
     
     
       14. The method of claim 7 wherein the kinematic viscosity of the aqueous treatment fluid is between about 0.3 and about 6.5 centipoise-gallons/pound. 
     
     
       15. The method of claim 7 wherein said aqueous treatment fluid, Component (A) comprises a hydroxyalkylcellulose, Component (B) comprises a combination of a carboxymethylcellulose and a water-swellable extender, Component (C) comprises a sulfonated hydrocarbon compound or salt thereof, and Component (F), where present, comprises a nonionic, alkoxylated alcohol. 
     
     
       16. The method of claim 15 wherein Component (A) comprises a hydroxypropylcellulose, Component (B) comprises a combination of a carboxymethylcellulose and bentonite, Component (C) comprises a sodium salt of a sulfonated polynaphthalene and Component (F), where present, comprises an ethoxylated- alkanol or -alkylphenol. 
     
     
       17. The method of claim 7 wherein said aqueous treatment fluid, Component (A) comprises about 0.1 to about 1.5 percent, Component (B) comprises about 0.5 to about 4 percent, Component (C) comprises about 0.1 to about 2.5 percent, Component (E) comprises about 90 to about 98 percent and Component (F) comprises about 0 to about 2 percent of the combined weight of said components of said treatment fluid. 
     
     
       18. The method of claim 17 wherein Component (D) is present in an amount of about 1.5 percent to about 150 percent based on the combined weight of Components (A), (B), (C), (E) and (F).